Process for producing motor fuels



w. BQROSS ET A1.

PROCESS FOR PRODUCING AMOTOR FUELS Jan. 15, i946.

Filed NOV. l, 1941 1N VENTORS.

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1:0 mODU William B.oss -BY lennel'h Boldi' 540V( A( M7 ATTORNEY.

Patented Jan. 15, 1946 www PROCESS FOR PRODUCING MOTOR FUELS William B. Ross, Evanston, and Kenneth Boldt, Highland Park, lll., assignors to The Pure Gil- Company, Chicago, Ill., a corporation of Ohioy Application November 1, 1941, Serial No. 417,439

4 Claims.

This invention relates vto the manufacture of high anti-knock gasoline having unusually effective road performance in internal combustion engines at both high and low speeds and more specifically to an integration of steps which involve separately treating by purely thermal and catalytic steps, fractions obtained by fractionation of a relatively wide boiling range charging stock such as crude oil, particularly one in which the gasoline boiling constituents are present in relatively low proportions and are Vof the naphthenic type, to produce a high octane gasoline of well-balancedl boiling range having a high proportion of unsaturated hydrocarbons in the low boiling portion and a low proportion of unsat-` urated hydrocarbons in the high boiling portion.

Experience has shown that highly olefinic motor fuels have certain disadvantages with respect to their use in modern automotive engines. Their susceptibility to lead is low as compared with paraiiinic hydrocarbons. Furthermore, under high speed operating conditions, olenic hydrocarbons have a tendency to cause knocking when used in engines having a relatively high compression ratio.

It has been found that these disadvantages may be overcome and unusually effective allspeed performance and high lead susceptibility obtained by controlling the chemical composition-boiling range relationship in motor fuels. The preferred fuels are those fuels which are predominantly olefinic in character in the'low boiling portion, that is, that portion of the fuel boiling up to about 140 F. and in which the high boiling portion contains not more than a minor amount of aliphatic unsaturated hydrocarbons. The high boiling portion is that portion of the fuel boiling between approximately 235 F. and the end point of the fuel. The boiling points are determined using an apparatus having a packed fractionating column and in which a relatively high reflux ratio is employed. At the present time most commercial motor fuels have an end point of about 400 F. The' intermediate portion of the fuel may consist of hydrocarbons of any chemical structure so long as the octane number of this fraction is suiiiciently high to maintain a relatively high overall octane in the finished fuel. The intermediate portion of the fuel is that'portion which distills between approximately 140 F. and 235 F. Fuels which have the aforementioned chemical composition-boiling range relationship produce unusually effective road performance in modern internal combustion engines.

As used throughout this specification and in the claims, the term unsaturated hydrocarbons" does not include aromatichydrocarbons.

In a specific embodiment, the present invention comprises separating hydrocarbon mixtures of wide boiling range such as crude oil particularly naphthenic type crude oils containing relatively low proportions of gasoline boiling range hydrocarbons to produce gas, gasoline and residual cracking stock, supplying the residual cracking stock to a catalytic cracking step or a purely thermal vapor phasel `cracking step, separatingthe cracked products into gas, low boiling gasoline distillate, high boiling gasoline distillate, recycle stock boiling above gasoline boiling range and residuum, subjecting the high boiling gasoline distillate to hydroforming, separating .the hydroformed products into gas and gasoline, subjecting said last-mentioned gas together with gas obtained from the cracking step and gas from the initial fractionating step to fractionation whereby tov separate a light gas consisting largely of hydrogen, methane and ethane and a heavy gas fraction consisting predominantly of Cs and C4 hydrocarbons, withdrawing thelight gas fraction from the system, subjecting the C3C4 fraction to catalytic or purely thermal polymerization and separating the conversion products into gas and gasoline and blending gasoline obtained from the polymerization process, gasoline from the hydroforming step, lo-W boiling gasoline from the cracking process and gasoline from the initial crude oil separation step to produce a finished motor fuel.

An object of this invention is to provide a unitary process for producing a well-balanced motor fuel capable of producing unusually effective performance in modern internal combustion engines at all engine speeds.

Another object of this invention is to produce motor fuels of high anti-knock rating and smooth curve boiling range having a predominant proa high proportion of the hydrocarbons in producing a high octane motor fuel having unusually effective performance characteristics.

A still further object of the invention is to provide a method for improvingthe performance Vmatic flow sheet; illustrating the process of the invention in such a manner as to eliminate unnecessary complications of processing details of each specific step, since those skilled in the art are now familiar with these details.

Referring to the accompanying drawing, crude oil is charged to the fractionation zone II and separated by fractionation into a gas fraction I 3, a gasoline fractionV I5 and a residual cracking stock fraction I 'I.

The gasoline fraction is ordinarily of about 100 to 400 F. boiling range and when the crude oil charged to the -process is a Gulf Coast type crude oil, to which this process is particularly applicable, the gasoline fraction will ordinarily comprise a relativelyl small proportion of the fractionation products and will be of relatively high octane value. This fraction may, therefore, be blended without further treatment with other gasoline fractions produced in the process as subsequently described, to form the desired composite motor fuel.

Y Residual cracking stock I1, which is ordinarily at relatively high temperature as a result of the initial fractionating step, is supplied to a cracking zone IS and therein subjected to suitable conditions of time, temperature and pressure to produce conversion products containing substantial proportions of high octane hydrocarbons of gasoline boiling range. The cracking process employed may be either purely thermal vapor phase or catalytic. Various. catalytic cracking processes are known and that process may be selected which produces a gasoline containing the lowest proportion of unsaturated hydrocarbons in the high boiling fraction and the highest proportion of unsaturated yhydrocarbons Vin the low boiling fraction. Suitable catalytic crackingprocesses` include the so-called Houdry process and the C. R.. A. process. The Houdry cracking process is described in numerous patents of the prior art such as, for example, Patent No. 2,161,676. The C. R. A. cracking process is particularly suitable for producing motor fuel hydrocarbons of the desired chemical composition in accordance with this invention and is adapted particularly well to operate in conjunction with the other operationsdescribed herein. In accordance with the operating conditions employed in the C. R. A. cracking process, the residual cracking stock is subjected to suificient heat to vaporize a substantial portion of the hydrocarbons, the Vaporized hydrocarbons separated from unvaporized residue, admixed with steam and catalyst and brought to a conversion temperature of the orderfof 950 F. The pressure employedr in the reaction `zone is of the order of V lbs. per sq. in. A process of this type is covered by the patent to Miller No. 1,799,858. Very finely divided catalyst such as silica,

lalumina or activated clays is employed and is maintained in suspension inthe mixture of vaporized hydrocarbons admixed with a relatively small quantity of steam in a reaction zone and the entire mixture retained in the reaction zone for a sufficient time to produceA substantial proportions of high octane conversion products of motor fuel boiling range. The solid catalyst is removed by means of cyclone precipitators or collectors from the efliuent from the reaction zone, the steam condensed and the hydrocarbon vapors fractionated. In the event that a purely thermal vapor phase cracking step is employed instead of the catalytic cracking step just described, the cracking stock is heated to rapidly vaporize a substantial portion of the stock and the vapors maintained at temperatures of the iorder of 1000 to 1500 F. under relatively low superatmospheric pressure for a sufficient period of time to effect the desired conversion. Such a thermal vapor phase cracking process is more completely described in Greenstreet Patent No. 1,886,093. The conversion products of such processes contain a high proportion of unsaturated hydrocarbons in the low boiling fraction. Gonversion products from the catalytic or purely thermal vapor phase cracking step I9 are separated into gas 2|, low boiling gasoline distillate 23, preferably having an end point of about 235 F., high boiling gasoline distillate 25, which ordinarily has a. boiling range of about 235 to 425 F., recyclestock 21 consisting of hydrocarbons boiling above gasoline boiling range and residuum 29. `Low boiling gasoline distillate 23 is blended with gasoline fractions obtained from other steps of the process to produce the desired composite gasoline. The high boiling gasoline fraction 25 may similarly be directly blended with other gasoline fractions to produce a finished gasoline or in the -event that this fraction contains an undesirably large proportion of unsaturated hydrocarbons, the fraction is supplied to catalytic hydroforming zone 3| wherein the distillate in admixture with hydrogen is contacted with suitable catalysts such as oxides of metals ofthe third, fth or sixth groups of the Periodic Table alone or on supports such as activated alumina, silica or pumice at temperatures of about 950 to l050 F. and pressures of approximately 300 to3000 lbs. per sq. in. to convert a substantial proportion of the distillate charged into cyclic, usually aromatic, hydrocarbons of the single-ring type boiling within the range of the high boiling portion of gasoline. Further details of such a hydroforming process are set forth in Pier et al. Patent No. Y2,045,795. .It is, of course, apparent that when both the low boiling gasoline fraction 23 and the high boiling gasoline fraction 25 are suitable for direct blending to finished gasoline, there is no need of preparing separate fractions. In this event both fractions may be separated from' thecracked products as a single gasoline fraction boiling from about to 425? F. Con- Version products from the catalytic hydroforming step 3| are separated into gas 33 and gasoline distillate 35. Gasoline distillate 35 is blended with gasoline fractions obtained from other steps in the process to produce the desired composite gasoline. Y

Gas 2| obtained from the catalytic or thermal vapor phase cracking step I9 is mixed with gas I3 obtained from the initial crude oil fractionation step and the resultant gas mixture fracA tionated in fractionation zone 3l. When the hydroforming step 3| is used, gas from this operation is preferably also supplied to fractionation zone 3'I. The products of the fractionating step are separated into light gas 39 consisting chlefiy of hydrogen, methane and ethane is withdrawn from the system and a heavy gas frac- 'tion #I consisting largely of Ca and C4 hydrooarbons which are supplied to `conversion zone 43 wherein catalytic Aor purely thermal polymerization is -eected Catalytic polymerization of the heavy gas fraction may be effected by contacting the gases yat temperatures of the order of 50'to 500 F. in the presence of a suitable catalyst such as a phosphoric acid catalyst to convert a substantial portion of the hydrocarbons charged into high octane hydrocarbons of gasoline boiling range. Such a catalytic polymerization process is more completely described in Holm et al. Patent No. 2,186,021. A purely thermal polymerization process may also be used in which case the heavy gas fraction 4l is subjected to temperatures of the order of 850 to 1200 F. and superatmospheric pressures of about 500 to 2000 lbs. per sq. in. for a sufficient period of time to convert a substantial proportion of the hydrocarbons charged into high octane hydrocarbons of gasoline boiling range, all of which is described in greater detail in Wagner Patent No. 2,157,225. The conversion products of the catalytic or thermal polymerization step 43 are separated into gas 45 which is ordinarily withdrawn from the system although portions thereof may be returned to fractionation step 31 or conversion step 43, and gasoline distillate 4l which is blended with gasoline fractions obtained from other steps in the process to produce the desired composite gasoline.

It will be seen from a consideration of the foregoing description that a. process has been described wherein a high proportion of the hydrocarbons found in crude oil is eiiiciently utilized for producing a gasoline containing predominant proportions of unsaturates in the low boiling range and not more than minor proportions of unsaturates in the high boiling range, which gasolines have been found capable of producing unusually effective road performance in modern internal combustion engines,

The specic operating conditions which may be employed in successfully conducting the various steps of the process will vary considerably depending upon the type of crude oil charging stock employed, the particular composition of the fractions subjected to conversion in each of the individual cooperative steps and the specific type of catalyst employed in the catalytic conversion zones. Since the regulation of the operating condi-tions in each of the individual steps to accomplish the object herein set forth is within the skill of those working in the art, no attempt has been made to herein define the specific limits of satisfactory operating conditions. While the particular operations referred to in connection with the detailed description of the invention have been described in connection with the processing of a Gulf Coast type crude oil containing a relatively low proportion of rela.- tively high octane gasoline, it is apparent that the process is broadly applicable to crude oils of various types.

Although reference has been made to specic patents in connection with various steps in the process, it should be understood that the patents have been cited as being merely illustrative of the particular steps. For example, other methods are known for the polymerization of normally gaseous hydrocarbons. The same is true of the hydroforming and catalytic cracking steps. The

various ,steps in the -process are limited;A 'therefore, only by the following definitions: i

'Catalytic cracking-A process for thermally converting higher 'boiling hydrocarbons into gasoline boiling hydrocarbons in the presence of a catalyst. l

'Thermal vvapor phase cracking-A process 'for converting higher boiling hydrocarbons in the vapor .state into gasoline boiling hydrocarbons by purely thermal means, i. e., without the use of a catalyst.

Hydroforming.-A process for catalytically converting non-aromatic hydrocarbons boiling approximately Within the gasoline range into alkylated cyclic hydrocarbons boiling approximately within the gasoline boiling range.

Catalytic polymerization-A process for converting normally gaseous hydrocarbons into gasoline boiling range hydrocarbons in the presence of a catalyst.

Thermal polymerization-A process for converting normally gaseous hydrocarbons into hydrocarbons of gasoline boiling range by purely thermal means, i. e., without the use of a catalyst.

While the invention has been shown and described in connection with a specic form of the invention, it will be understood that the invention is not limited to these conditions and is limited only as defined in the following claims.

We claim:

1. The process for preparing gasoline from. crude petroleum oil poor in gasoline fractions which comprises separating said oil into gas, gasoline and residual cracking stock, subjecting the cracking stock to a cracking operation in the presence of a catalyst of the type selected from the group consisting of silica, alumina and activated clays at a temperature of the order of 950 F. suitable for converting said stock into high octane gasoline boiling range hydrocarbons, separating gas, low boiling gasoline distillate and high boiling gasoline distillate from the conversion products, withdrawing the low boiling gasoline distillate from the process, catalytically hydroforming the high boiling gasoline under pressure at temperatures of approximately 950 to 1050c F. in the presence of hydrogen subjecting higher boiling constituents in the rst-mentioned gas and in gas obtained from the cracking operation to polymerization whereby to convert said constituents into hydrocarbons of gasoline boiling range, separating gasoline from the conversiou products and combining the gasoline from the initial crude oil separating step, low boiling gasoline distillate fromA the cracking operation and gasoline from the polymerization operation, gasoline from the hydroforming step to make a composite gasoline.

2. Process in accordance with claim 1 in which the polymerization operation is a thermal operation.

3. Process in accordance with claim 1 in which the polymerization operation is a catalytic operation.

4. In a process for converting crude oil into gasoline of high anti-knock quality the steps of subjecting a fraction of said oilboiling above the gasoline range to cracking in the presence of a catalyst of the type selected from the group consisting of silica, alumina and activated clays at a temperature of the order of 950 F. whereby to produce a low boiling gasoline fraction having a high proportion of unsaturated hydrocarbons, separating said low-boiling gasoline fraction, also line with the low boiling cracked gasoline, fraction and gasoline from said hydroforming step to produce a finished gasoline in which the portion boiling up to 140 F. is predominantly olefinic and the portion boiling above 235 F. contains a minor portion of olens and is rich in alkylated cyclic hydrocarbons. Y f

' WILLIAM B. ROSS.-

KENNETH BOLD'I',r 

